If after you've checked everything and it still leaks, then you may want to get clamps to go around the pipe at the fitting. Brs sells them. I use them for the pump side of the hose.
http://www.bulkreefsupply.com/ratchet-clamp-for-tubing-1-6684828461f4e5bda1e2a33b5e0db6d3.html
http://www.bulkreefsupply.com/ratchet-clamp-for-tubing-1-6684828461f4e5bda1e2a33b5e0db6d3.html